Piezoelectric actuated poppet valve to modulate pilot pressures and control main valve activation

ABSTRACT

A piezoelectric actuated poppet valve is disclosed. The piezoelectric valve generally includes a valve body having multiple passages that provide fluid flow paths through the valve body. Flow through the flow paths is controlled by the position of a poppet valve that is slidably received in a fluid-tight manner in an interior space within the valve body. A piezoelectric actuator is secured to the valve body and contacts the poppet valve. Actuation of the piezoelectric actuator moves the poppet valve within the interior space. Movement of the poppet valve within the interior space controls flow through the fluid flow paths in the valve body.

This is a divisional application of application Ser. No. 09/314,063,filed May 18, 1999.

TECHNICAL FIELD

This invention relates generally to hydraulic valves, and, morespecifically, to the control of a hydraulic valve by a piezoelectricactuated poppet valve.

BACKGROUND ART

Piezoelectric materials respond to exposure to an electrical field bydeforming in a manner that varies directly with the applied potentialdifference. The direction of deformation, namely an increase or adecrease in length, is dependent on the polarity of the electrical fieldand the arrangement of the piezoelectric material. Generally, apiezoelectric element is formed by stacking a series of discs of thepiezoelectric material wherein the discs are interweaved with electrodesto enable the discs to be exposed to an electrical field.

Piezoelectric elements have the advantage of being able to sustain veryhigh cycle frequencies and to respond nearly instantaneously to a changein the electrical field. By way of example, a piezoelectric elementformed of a properly oriented stack of discs can respond to a negativepolarity by expanding along a longitudinal axis of the stack of discswithin microseconds. For example, a stack of discs approximately 150 mmlong will expand approximately 75 μm.

In a typical hydraulic control system, a hydraulic valve includes aninternal spool having at either end of it a control volume. Highhydraulic pressure is metered into each of the control volumes at eachend of the spool. Movement of the spool is used to control the output ofthe hydraulic valve. Movement of the spool within the hydraulic valve isoften accomplished by modulation of a pilot pressure, which is also fedinto each control volume at each end of the spool. The pilot pressure isunder a lower pressure than the high hydraulic pressure. Thus, movementof the spool within the hydraulic valve can be accomplished by smallchanges in the pilot pressure at either end of the spool. Typically,operator input is used to regulate the pilot pressure to either end ofthe spool in order to effect movement of the spool within the valvewhich in turn causes movement of, for example, a machine implement.

One disadvantage with current hydraulic valves is their response time tooperator input. It would be advantageous to have a hydraulic valve thatresponded nearly instantaneously to operator inputs. The very rapidresponse time of piezoelectric materials makes them ideal candidates forincorporation into a hydraulic control valve system.

The present invention is directed to overcoming one or more of theproblems set forth above.

DISCLOSURE OF THE INVENTION

In one aspect of this invention, a piezoelectric valve is disclosed. Thepiezoelectric valve includes a valve body having a first end opposite asecond end, first multiple passages in fluid communication with a firstchamber adjacent the first end and second multiple passages in fluidcommunication with a second chamber adjacent the second end, an interiorspace defined between the first chamber and the second chamber, a poppetvalve received within the interior space in a fluid tight fit andslideable within the interior space, the poppet valve having a first endopposite a second end, a piezoelectric actuator contacting the poppetvalve, the piezoelectric actuator sliding the poppet valve within theinterior space when the piezoelectric actuator is actuated, a springbiasing the second end of the poppet valve into a valve seat when thepiezoelectric actuator is not actuated and permitting fluid flow throughthe first multiple passages and the first chamber, thereby establishinga first fluid flow path through the valve body, the spring preventingfluid flow through the second multiple passages and the second chamber,and actuation of the piezoelectric actuator moving the poppet valve awayfrom the valve seat and compressing the spring to permit fluid flowthrough the second multiple passages and the second chamber therebyestablishing a second flow path through the valve body and preventingfluid flow through the first flow path.

In another aspect of this invention, a method for controlling flow offluid through a valve body is disclosed. The method includes the stepsof providing a valve body having a first chamber and a second chamberwith an interior space defined between the first and second chambers,providing first multiple passages through the valve body and in fluidcommunication with the first chamber and second multiple passagesthrough the valve body and in fluid communication with the secondchamber, positioning a poppet valve within the interior space in aslideable and fluid-tight fit, positioning a piezoelectric actuator tocontact the poppet valve, biasing the poppet valve in a first directionwhen the piezoelectric actuator is not actuated, thereby permittingfluid flow through the first multiple passages while preventing fluidflow through the second multiple passages, and actuating thepiezoelectric actuator to move the poppet valve in a second directionopposite the first direction to thereby permitting fluid flow throughthe second multiple passages while preventing fluid flow through thefirst multiple passages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference may bemade to the accompanying drawings in which:

FIG. 1 is a schematic view of a hydraulic control system incorporatingpiezoelectric valves designed in accordance with the present invention;

FIG. 2 is a cross-sectional view of a piezoelectric valve designedaccording to the present invention;

FIG. 3 is a cross-sectional view of another piezoelectric valve designedaccording to the present invention; and

FIG. 4 is a cross-sectional view of another piezoelectric valve designedaccording to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A schematic view of a hydraulic control system is generally indicated bynumeral 20 in FIG. 1. The hydraulic control system 20 is used to controla variety of implements on a machine and machine functions.

Hydraulic control system 20 includes a number of hand controls 22 fortranslating movement of an operator's hands into movement of animplement. Generally, hand controls 22 comprise electronic hand controlsthat transform movements of an operator's hands into electrical signalsthat are sent to an electronic control computer 24. Electronic computer24 receives the electrical signals from hand controls 22 and transmitscontrolled electrical signals to a variety of actuators including aplurality of piezoelectric valves 32.

A hydraulic pump 26 takes in rotary motion from an engine (not shown)and puts out high hydraulic pressure. Hydraulic pump 26 is connected toa hydraulic reservoir (not shown) as is known in the art. Hydraulicvalves 28 receive the high hydraulic pressure from hydraulic pump 26 andcontrolled low pilot pressure from piezoelectric valves 32. As discussedabove, hydraulic valves 28 include a spool (not shown) and controlvolumes at each end of the spool. High hydraulic pressure from hydraulicpump 26 and low pilot pressure from piezoelectric valves 32 are fed intoeach control volume to control the position of the spool in thehydraulic valve 28. Hydraulic pump 26 sends high hydraulic pressure to ahydraulic pressure-reducing valve 30 which puts out the lower pilotpressure to piezoelectric valves 32. Movement of hydraulic valves 28 iscontrolled by modulation of the pilot pressure supplied frompiezoelectric valves 32.

Hydraulic valves 28 put out controlled high pressure to a plurality ofhydraulic actuators 34 such as motors and hydraulic cylinders. Hydraulicactuators 34 take in the controlled high hydraulic pressure fromhydraulic valves 28 and exert mechanical force to move mechanicalmachine parts and implements 36. Small changes in pilot pressure ineither of the control volumes of hydraulic valve 28 can be utilized toshift the spool in hydraulic valve 28 in a first direction or a seconddirection. Shifting of the spool in hydraulic valve 28 causes themovements in mechanical machine parts and implements 36.

Referring now to FIG. 2, a piezoelectric valve designed according to thepresent invention is shown generally indicated by numeral 32.Piezoelectric valve 32 includes a valve body 40 having a first end 42and a second end 44 that is opposite the first end 42. Piezoelectricvalve 32 further includes a poppet valve 46 and a piezoelectric actuator48.

First end 42 of valve body 40 includes a threaded aperture 50 forreceiving a hollow bolt 52. Hollow bolt 52 comprises a head 54 adjacenta cylindrical portion 56 having external threads 57. Cylindrical portion56 with external threads 57 is received in threaded aperture 50.Cylindrical portion 56 further includes a passage 58. A seal 60 isreceived between head 54 and hollow bolt 52 to seal one end of a firstchamber 64, a portion of which is formed in cylindrical portion 56. Aspring recess 62 adjacent first chamber 64 receives one end of a spring66.

A first passage 68 in valve body 40 is in communication with passage 58in cylindrical portion 56. Passage 58 permits communication betweenfirst passage 68 and first chamber 64. Additionally, first passage 68communicates with a second passage 70 adjacent second end 44 of valvebody 40.

Valve body 40 further includes a third passage 72 adjacent second end44. Third passage 72 is in fluid communication with a second chamber 108adjacent second end 44 of valve body 40. Valve body 40 further includesan interior space 74 between first end 42 and second end 44. Interiorspace 74 receives poppet valve 46.

Poppet valve 46 includes a first end 76 and a second end 78 oppositefirst end 76 with a body 79 between them. A first recess 80 is locatedin first end 76 and receives a portion of a spring 66. First end 76further includes a first beveled surface 82. Second end 78 includes asecond beveled surface 84. An actuator recess 86 extends from second end78 into body 79. Actuator recess 86 is for receiving a portion ofpiezoelectric actuator 48. Poppet valve 46 is slideable within interiorspace 74 in a fluid-tight manner.

The second end 44 of valve body 40 includes a threaded aperture 88 forreceiving a portion of piezoelectric actuator 48. Piezoelectric actuator48 comprises a hollow bolt 90 having a head 92, a threaded portion 94,and a sleeve 96. Threaded portion 94 is received in threaded aperture88. Sleeve 96 extends into actuator recess 86 of poppet valve 46. Sleeve96 receives a piezoelectric element 98. The piezoelectric element 98 ispreferably embedded or potted in the sleeve 96 with sealing material,e.g., plastic, that provides protection and allows the hollow bolt 90,head 92, threaded portion 94, and a sleeve 96 to function as an assemblyto form the piezoelectric actuator 48.

Piezoelectric element 98 is connected to a pair of wire leads 100. Wireleads 100 receive electric signals from electronic control computer 24to actuate or deactuate the piezoelectric actuator 48.

Piezoelectric element 98, as discussed above, generally comprises astack of disks of piezoelectric material, such as lead zirconatetitanate. Piezoelectric element 98 is formed of a stack of these disksinterweaved with electrodes (not shown) connected to wire leads 100.Actuation of the piezoelectric actuator 48 causes piezoelectric element98 to expand or contract along its longitudinal axis depending on thepolarity of the electrical signal and the arrangement of the disks.

A jam nut 102 is received on threaded portion 94 to secure piezoelectricactuator 48 relative to second end 44 and poppet valve 46. A washer 104and a seal 106 are received adjacent jam nut 102 and serve to sealthreaded aperture 88 from the outside elements. Piezoelectric actuator48 extends through second chamber 108. Second chamber 108 includes avalve seat 110 for receiving second beveled surface 84 of poppet valve46.

Spring 66 normally biases poppet valve 46 into valve seat 110 in theposition, shown in FIG. 2, when piezoelectric actuator 48 is notactuated. That is, normally second beveled surface 84 is against valveseat 110 thus preventing fluid communication through third passage 72,second chamber 108 and second passage 70. First passage 68 is normallyin fluid communication with first chamber 64 and second passage 70 thusproviding a first flow path through valve body 40.

In a preferred embodiment, applying an electrical current through wireleads 100 to piezoelectric actuator 48 causes piezoelectric element 98to expand along its longitudinal axis. For example, a 150 mm longpiezoelectric element 98 will generally have a stroke length ofapproximately 75 μm. Movement of this amount is sufficient to movepoppet valve 46 and push first beveled surface 82 against cylindricalportion 56 thereby preventing fluid flow through the first flow path. Inaddition, this movement of poppet valve 46 toward first end 42 opensfluid communication between second passage 70, second chamber 108, andthird passage 72 thereby creating a second flow path through valve body40.

Once the electric current to piezoelectric actuator 48 is turned off andthe charge placed on the piezoelectric material is bleed-off anddischarged, spring 66 returns poppet valve 46 to the position, shown inFIG. 2, thereby opening first flow path and closing second flow path.

The disclosed piezoelectric valve 32 could be used in a number of waysin hydraulic control system 20 to control, for example, the distributionof pilot pressure. In one use, each control volume of the spool inhydraulic valve 28 would be in fluid communication with second passage70 of piezoelectric valve 32 and pilot pressure would be supplied tofirst passage 68 of piezoelectric valve 32. Thus, initially the spoolwould be centered within hydraulic valve 28 because each end of thespool would be receiving the same pilot pressure from its associatedpiezoelectric valve 32. Third passage 72 would be connected to thehydraulic fluid reservoir. To shift the spool within hydraulic valve 28one of the piezoelectric valves 32 would be actuated throughpiezoelectric actuator 48. Actuation of a piezoelectric valve 32 causespoppet valve 46 to shift toward first end 42 of valve body 40, therebyclosing the first flow path and opening the second flow path. Thus,permitting an outflow of pressure from the associated control volume ofthe spool in hydraulic valve 28 to the hydraulic pump reservoir (notshown) through the second flow path. Turning off electrical actuation ofpiezoelectric actuator 48 enables spring 66 to return poppet valve 46 tothe position shown in FIG. 2 thus stabilizing the spool in hydraulicvalve 28 at a new position.

In FIG. 3, a cross-sectional view of an alternative embodiment of apiezoelectric valve is generally shown by numeral 116. Piezoelectricvalve 116 includes a valve body 118 having a first end 120 opposite asecond end 122. An interior space 123 is located within valve body 118.Interior space 123 receives a poppet valve 124, which is slideablewithin interior space 123 in a fluid-tight manner.

Second end 122 of valve body 118 includes a threaded aperture 126 forreceiving cylindrical portion 94 of piezoelectric actuator 48.Piezoelectric actuator 48, shown in FIG. 3, functions identically to thepiezoelectric actuator 48, shown in FIG. 2.

First end 120 includes a threaded aperture 128 for receiving a plug 130.Plug 130 includes a head 132 adjacent a cylindrical portion 134.Cylindrical portion 134 is received in threaded passage 128. A seal 135is received between head 132 and first end 120 to seal threaded aperture128 from the outside elements.

A spring recess 136 is located within cylindrical portion 134 andreceives a portion of a spring 138. Spring 138 biases poppet valve 124toward second end 122.

Valve body 118 includes a first passage 140 that is in fluidcommunication with a second passage 142, a second chamber 158 and athird passage 160. Second passage 142 is in fluid communication with afirst chamber 144 defined by spring recess 136 and poppet valve 124.

Poppet valve 124 includes a first end 146 having a boss 148 forretaining spring 138. Opposite first end 146 is a second end 150. A body152 joins first end 146 to second end 150. Second end 150 includes abeveled surface 154 and an actuator recess 156 for receiving sleeve 96and piezoelectric element 98 of piezoelectric actuator 48. The retainedspring 138 normally biases beveled surface 154 against a valve seat 162in valve body 118. Thus, normally there is no fluid communicationbetween first passage 140, second chamber 158, and third passage 160.

When piezoelectric actuator 48 is actuated by an electrical current,piezoelectric element 98 expands and moves poppet valve 124 toward firstend 120 of valve body 118. Thus, enabling fluid communication betweenthird passage 160, second chamber 158 and first passage 140.

In use, piezoelectric valve 116 can be used as a variable size orificeto provide either supply pilot pressure to a hydraulic valve 28 or toenable release of hydraulic pressure from a hydraulic valve 28. Thefunction of piezoelectric valve 116 will depend upon the portions of thehydraulic control system 20 that are connected to third passage 160 andfirst passage 140. In piezoelectric valve 116, a second passage 142permits equalization of pressure on both ends of poppet valve 124.

FIG. 4 is a cross-sectional view of an alternative embodiment of apiezoelectric valve 166. Piezoelectric valve 166 includes twopiezoelectric actuators 48 that are identical to those disclosed abovein FIG. 2 and FIG. 3.

Piezoelectric valve 166 includes a valve body 168 having a first end 170opposite a second end 172. An interior space 173 is located betweenfirst end 170 and second end 172. Interior space 173 receives a poppetvalve 174, which is slideable in a fluid-tight manner within interiorspace 173.

Second end 172 of valve body 168 includes a threaded aperture 176 forreceiving threaded portion 94 of piezoelectric actuator 48 in a mannersimilar to that shown in FIG. 2.

First end 170 includes a threaded passage 178 for receiving a plug 180.Plug 180 includes a head 182 adjacent a cylindrical portion 184.Cylindrical portion 184 is received within threaded aperture 178. A seal186 is received between head 182 and first end 170 to seal out outsideelements.

Plug 180 further includes a threaded aperture 192 for receipt ofthreaded portion 94 of piezoelectric actuator 48 in a manner similar tothat shown in FIG. 2. Cylindrical portion 184 includes a passage 188that is in fluid communication with a first chamber 190 located withincylindrical portion 184.

Valve body 168 includes a first passage 194 adjacent second end 172.First passage 194 is in fluid communication with a second passage 196, asecond chamber 202, and a fourth passage 200. Second passage 196 is influid communication with first chamber 190 and a third passage 198.

Poppet valve 174 includes a first end 204 opposite a second end 206.First end 204 and second end 206 are separated by a body 208. First end204 includes a first beveled surface 310 and second end 206 includes asecond beveled surface 312. A first actuator recess 314 extends fromfirst end 204 into body 208. First actuator recess 314 receives thesleeve 96 of a first piezoelectric actuator 48. A second actuator recess316 extends from second end 206 into body 208 and receives a sleeveportion 96 of a second piezoelectric actuator 48.

As shown in FIG. 4, interior space 173 and poppet valve 174 are sizedsuch that poppet valve 174 is centered in interior space 173 and thereis a first fluid flow path through valve body 168 between first passage194 and third passage 198, and a second fluid flow path through valvebody 168 between first passage 194 and fourth passage 200. Thus,piezoelectric valve 166 normally has two fluid flow paths. Actuation ofa first piezoelectric actuator 48 with a first electrical current causesexpansion of its piezoelectric element 98. Simultaneous actuation of thesecond piezoelectric actuator 48 with a second electrical current causescompression of its piezoelectric element 98. The net result is a shiftin poppet valve 174 toward either first end 170 or second end 172. Theshift closes off either the first or second flow path and further opensthe other flow path. Removing the electrical currents will allow poppetvalve 174 to return to a centered position, as shown in FIG. 4.

In use, third passage 198 may be connected to one control volume of aspool in hydraulic valve 28 while fourth passage 200 is connected to theother control volume of the spool in hydraulic valve 28. Pilot pressureand high hydraulic pressure would be supplied to both control volumes ofthe spool in hydraulic valve 28 by open orifices. First passage 194would be connected to the hydraulic fluid reservoir. Thus, when neitherpiezoelectric actuator 48 is activated, as shown in FIG. 4, there willbe a slow leak of hydraulic pressure from hydraulic valve 28 throughpiezoelectric valve 166, but the loss of hydraulic pressure fromhydraulic valve 28 will be equal on either side of the spool inhydraulic valve 28. Actuation of the piezoelectric actuators 48 by thefirst and second electrical currents will cause a shift in poppet valve174 thereby closing off one of the fluid flow paths from one of thecontrol valves of the spool in hydraulic valve 28 and increasing thefluid flow through the other flow path associated with the other controlvolume of the spool in hydraulic valve 28, thereby enabling spool ofhydraulic valve 28 to shift.

Industrial Applicability

A piezoelectric valve 32 enables a pilot pressure to a hydraulic valve28 to be modulated by an electrical input. Piezoelectric valve 32includes a valve body 40 having a plurality of passages that create aplurality of fluid flow paths through the valve body 40. A poppet valve46 is located within an interior space 74 within the valve body 40.Poppet valve 46 is slideable within interior space 74 in a fluid-tightmanner. Poppet valve 46 receives a piezoelectric actuator 48.Application of an electrical current to piezoelectric actuator 48 causespoppet valve 46 to shift within interior space 74 thereby opening somefluid flow paths and closing other fluid flow paths. The opening andclosing of flow paths permit flows into or out of control volumes oneither end of a spool located in a hydraulic valve 28 that is connectedto the piezoelectric valve 32. Thus, the present invention provides acompact and simple valve that can rapidly alter, for example, the pilotpressure supplied to a hydraulic valve 28 to control movement of a spoolwithin hydraulic valve 28 and thereby hydraulically shift a machine partor implement 36.

Other aspects, objects, and features of the present invention can beobtained from a study of the drawings, the disclosure, and the appendedclaims.

What is claimed is:
 1. A piezoelectric valve comprising: a valve bodyincluding a first end opposite a second end, a first plurality ofpassages in communication with a first chamber adjacent said first endand a second chamber adjacent said second end, and an interior spacedefined between and separating said first chamber with said secondchamber; a poppet valve is receivable in said interior space in a fluidtight fit and slidable within said interior space, said poppet valvehaving a first end opposite a second end with said first end extendinginto said first chamber and said second end extending into said secondchamber; a piezoelectric actuator is in contact with said second end ofsaid poppet valve, said piezoelectric actuator is capable of slidingsaid poppet valve within said interior space when said piezoelectricactuator is actuated; a spring located in said first chamber andcontacting said first end of said poppet valve to bias said second endof said poppet valve into a valve seat when said piezoelectric actuatoris not actuated and said second end of said poppet valve is capable ofpreventing fluid communication through said first plurality of passagesand said second chamber, wherein said piezoelectric actuator is actuatedthereby moving said second end out of said valve seat and compressingsaid spring to permit fluid flow through said first plurality ofpassages and said second chamber thereby creating a first fluid flowpath through said valve body.
 2. A piezoelectric valve as recited inclaim 1, wherein said poppet valve includes an actuator recess, saidactuator recess extends from said second end of said poppet valve towardsaid first end of said poppet valve, said actuator recess is capable ofreceiving said piezoelectric actuator.
 3. A piezoelectric valve asrecited in claim 1, wherein said second end of said poppet valveincludes a beveled surface, said beveled surface is received in saidvalve seat.
 4. A piezoelectric valve as recited in claim 1, wherein saidsecond end of said valve body includes a threaded aperture and saidpiezoelectric actuator includes a piezoelectric element, a jam nut and ahollow bolt having a head, a threaded portion and a sleeve and saidpiezoelectric element is receivable in said sleeve and said threadedportion is engageable with said threaded aperture and said jam nut ispositioned on said threaded portion adjacent second end of said valvebody to secure said piezoelectric actuator to said second end of saidvalve body.
 5. A piezoelectric valve as recited in claim 4, furthercomprising a seal position between said jam nut and said second end ofsaid valve body.
 6. A piezoelectric valve as recited in claim 4, furthercomprising a plurality of wire leads extending through said head of saidhollow bolt to said piezoelectric element with said wire leads forproviding electrical power to actuate said piezoelectric actuator.
 7. Apiezoelectric valve as recited in claim 1, wherein said first end ofsaid valve body includes a threaded aperture and said threaded apertureis capable of receiving a plug having a head and a cylindrical portionand said cylindrical portion defines a chamber and includes externalthreads that are engageable with said threaded aperture to secure saidplug in said threaded aperture.
 8. A piezoelectric valve as recited inclaim 7, wherein said cylindrical portion further includes a springrecess for receiving a portion of said spring and said valve bodyincludes a passage in fluid communication with said chamber.